It is commonly required to personalize a web document for each user who views the document. Such personalization might involve an advertisement that is targeted on the basis of the preferences of the user, or information such as quotes for stocks in the user's portfolio etc. Furthermore, it is also commonly required to update pages that a user or a group of users has previously viewed with fresh information on stock prices, news etc. In either case, the web document requested by the user comprises content that is common to another web document previously delivered to the same user or other users, as well as content that is new and possibly particularized to the user. Furthermore, the common content typically forms the majority of the bytes in the document. In other words, only a small percentage of the document changes between subsequent downloads.
In the background art (see, e.g., U.S. Pat. No. 6,178,461), it is known to encode web documents as variations of previously delivered documents that require explicit action on the part of the user's content browser. In particular, the user's content browser selects one or more objects from its cache that it expects to be similar to the current document and includes references to these documents when requesting the current document from the content server. The difficulty with this browser-driven approach is that it requires millions of content browsers to be upgraded to include this modification. Furthermore, it requires that the server have access to the millions of old documents previously transmitted to the users in order to correctly recover the base documents referenced in each request.
Another approach was disclosed in co-pending U.S. patent application Ser. No. 09/634,134, filed on Aug. 8, 2000, which is hereby incorporated by reference in its entirety. That application disclosed general techniques for transmitting the incremental differences between successive downloads of web documents were disclosed. In the present application, we expand upon those teachings.